Supporting base



FIG. 1 is a perspective view of a supporting base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left elevational view thereof;

FIG. 5 is a right elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is the perspective view embodying the utilization of supportingbase in which the broken line is for illustrative purposes only andforms no part of the claimed design.

The ornamental design for supporting base, as shown and described.